U
- U-Foes in Incredible Hulk #254
- Ulik in Thor #137
- Ultron in Avengers #54
- Umar in Strange Tales #150
- Unus the Untouchable in X-Men #8
- Uni-Mind in Eternals #12
- Unicorn in Tales of Suspense #56
- Union Jack
- I: in Invaders #7
- II: in Invaders #20
- III: in Captain America #254
- Ursa Major in Incredible Hulk #258
- U.S. Agent in Captain America #323
Read more about this topic: List Of First Appearances In Marvel Comics Publications